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This study was aimed to evaluate the pattern of cellulase biosynthesis from Aspergillus fumigatus ABK9 under submerged fermentation. Production was increased concomitantly with fungal growth up to 72 h and reached maximum (Xmax –6.72 g/l) with specific growth rate (µmax) of 0.126/h. Highest specific rate of enzyme production (qp) was found at initial medium pH of 5.0 and incubation temperature of 30°C. At the same time, in the presence of 2-deoxy-D-glucose concentration of 0.5 mg/ml, the production of cellulolytic enzymes, viz, carboxymethyl cellulase activity (CMCase), filter paper degrading activity (FPase) and β-glucosidase activity reached maximum of 132.2, 21.3 and 28.9 U/ml, respectively. Cellulase biosynthesis was induced in respect to higher volumetric production rate (Qp), specific rate of enzymes production (qp, U/g biomass/h) and enzyme/biomass yield (YE/X) when grown in carboxymethyl cellulose in comparison to other saccharides as sole carbon source. Induction ratios (IR) of cellulases were between 12.3 and 24.4 in the presence of 1.5% (w/v) CMC in the culture media. The strain was quite resistant to catabolic repression by glucose up to 0.4% (w/v). Cellulases production was greatly influenced in the presence of yeast extract and potassium dihydrogen phosphate (KH₂PO₄) as nitrogen and phosphate sources in the culture media. C/N ratio of 10.0 and C/P ratio of 4.0 proved to be the best for the production of enzyme cocktail. Along with the high production yield, the crude enzymes showed a promising cellulose hydrolyzing efficiency of rice straw, indicating the enzyme could be beneficial for its large scale industrial exploitation.
The present report describes the new occurrence of Tomato mosaic virus (ToMV) in cabbage, bean and Malva neglecta plants in Iran. In this study, sequence analyses of a partial RNA dependent RNA polymerases (RdRp) and complete movement protein (MP) and the coat protein (CP) nucleotide sequences of three new ToMV isolates collected from major crop fields in Iran revealed low genetic variation of RdRp gene compared to the CP and MP genes. The different topologies of the phylogenetic trees constructed, using available open reading frame (ORF1), ORF2 and ORF3 sequences from ToMV isolates, indicated different evolutionary constraints in these genomic regions. Statistical analysis also revealed that with the exception of CP other tested ToMV genes were under negative selection and the RdRp gene was under the strongest constraints. According to the phylogenetic tree it can be inferred from the nucleotide sequences of the complete CP and MP genes, that isolates from Iran and Egypt formed separate groups, irrespective of host origin. However, isolates clustered into groups with correlation to geographic origin but not the host. Analysis of the Ks*, Z* and Snn values also indicated genetic differentiation between ToMV populations. The Tajima’s D, Fu and Li’s statistical values were significantly negative for the RdRp gene of the Asian population which suggests the sudden expansion of ToMV in Asia. Taken together, the results indicate that negative selection and genetic drift were important evolutionary factors driving the genetic diversification of ToMV.
A new isolate (BEH) of entomopathogenic fungus, Beauveria bassiana was isolated from soil using DOC2 selective medium. This isolate was characterized by conidiophores consisting of whorls and dense clusters of short conidiophorous cells with one-celled spherical conidia. Conidial length and width were 2.27±0.22 μm and 1.85±0.32 μm, respectively with length/width ratio of 1.23. Colonies on SDYA medium were normally white to pale yellow and sometimes red pigmented in reverse. Because of importance of this pathogen in biocontrol programs around the world and difficulties with morphological identification, a molecular technique was developed to assist complementary identification of the fungus. Pr1, a pathogenicity-related alkaline cuticle-degrading serine protease, with defined sequence in B. bassiana was amplified using PCR technique. The presence of this gene in isolated fungus (BEH) with 744 bp sequence length, as visualized on agarose gel affirmed the data from morphological studies that the new isolate (BEH) pertained to entomopathogenic fungus, B. bassiana. Pathogenicity of new isolate against Tenebrio molitor and its recovering was the other confirmation that the isolated fungus belonged to B. bassiana, using further light microscope studies.
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